First systematic review of the last 30 years of research on sweetpotato: elucidating the frontiers and hotspots.

Sweetpotato is an economically important crop, and it has various advantages over other crops in addressing global food security and climate change. Although substantial articles have been published on the research of various aspects of sweetpotato biology, there are no specific reports to systematically crystallize the research achievements. The current review takes the lead in conducting a keyword-centric spatiotemporal dimensional bibliometric analysis of articles on sweetpotato research using CiteSpace software to comprehensively clarify the development status, research hotspot, and development trend in the past 30 years (1993-2022). Quantitative analysis was carried out on the publishing countries, institutions, disciplines, and scholars to understand the basic status of sweetpotato research; then, visual analysis was conducted on high-frequency keywords, burst keywords, and keyword clustering; the evolution of major research hotspots and the development trend in different periods were summarized. Finally, the three main development stages-preliminary stage (1993-2005), rapid stage (2006-2013), and diversified mature stage (2014-2022)-were reviewed and analyzed in detail. Particularly, the development needs of sweetpotato production in improving breeding efficiency, enhancing stress tolerance, coordinating high yield with high quality and high resistance, and promoting demand were discussed, which will help to comprehensively understand the development dynamics of sweetpotato research from different aspects of biological exploration.

A Small Auxin-Up RNA Gene, IbSAUR36, Regulates Adventitious Root Development in Transgenic Sweet Potato.

Small auxin-upregulated RNAs (SAURs), as the largest family of early auxin-responsive genes, play important roles in plant growth and development processes, such as auxin signaling and transport, hypocotyl development, and tolerance to environmental stresses. However, the functions of few SAUR genes are known in the root development of sweet potatoes. In this study, an IbSAUR36 gene was cloned and functionally analyzed. The IbSAUR36 protein was localized to the nucleus and plasma membrane. The transcriptional level of this gene was significantly higher in the pencil root and leaf.This gene was strongly induced by indole-3-acetic acid (IAA), but it was downregulated under methyl-jasmonate(MeJA) treatment. The promoter of IbSAUR36 contained the core cis-elements for phytohormone responsiveness. Promoter ß-glucuronidase (GUS) analysis in Arabidopsis showed that IbSAUR36 is highly expressed in the young tissues of plants, such as young leaves, roots, and buds. IbSAUR36-overexpressing sweet potato roots were obtained by an efficient Agrobacterium rhizogenes-mediated root transgenic system. We demonstrated that overexpression of IbSAUR36 promoted the accumulation of IAA, upregulated the genes encoding IAA synthesis and its signaling pathways, and downregulated the genes encoding lignin synthesis and JA signaling pathways. Taken together, these results show that IbSAUR36 plays an important role in adventitious root (AR) development by regulating IAA signaling, lignin synthesis, and JA signaling pathways in transgenic sweet potatoes.

Overexpression of phosphatidylserine synthase IbPSS1 enhances salt tolerance by stimulating ethylene signaling-dependent lignin synthesis in sweetpotato roots.

Phosphatidylserine (PS) is an important lipid signaling required for plant growth regulation and salt stress adaptation. However, how PS positively regulate plant salt tolerance is still largely unknown. In this study, IbPSS1-overexpressed sweetpotato plants that exhibited overproduction of PS was employed to explore the mechanisms underlying the PS stimulation of plant salt tolerance. The results revealed that the IbPSS1-overexpressed sweetpotato accumulated less Na+ in the stem and leaf tissues compared with the wild type plants. Proteomic profile of roots showed that lignin synthesis-related proteins over-accumulated in IbPSS1-overexpressed sweetpotato. Correspondingly, the lignin content was enhanced but the influx of Na + into the stele was significantly blocked in IbPSS1-overexpressed sweetpotato. The results further revealed that ethylene synthesis and signaling related genes were upregulated in IbPSS1-overexpressed sweetpotato. Ethylene imaging experiment revealed the enhancement of ethylene mainly localized in the root stele. Inhibition of ethylene synthesis completely reversed the PS-overproduction induced lignin synthesis and Na+ influx pattern in stele tissues. Taken together, our findings demonstrate a mechanism by which PS regulates ethylene signaling and lignin synthesis in the root stele, thus helping sweetpotato plants to block the loading of Na+ into the xylem and to minimize the accumulation of Na+ in the shoots.

Genome-Wide Identification and Expression Analysis of the DMP and MTL Genes in Sweetpotato (Ipomoea batatas L.).

Sweetpotato (Ipomoea batatas L.) is a strategic crop with both economic and energy value. However, improving sweetpotato varieties through traditional breeding approaches can be a time-consuming and labor-intensive process due to the complex genetic nature of sweetpotato as a hexaploid species (2n = 6x = 90). Double haploid (DH) breeding, based on in vivo haploid induction, provides a new approach for rapid breeding of crops. The success of haploid induction can be achieved by manipulating specific genes. Two of the most critical genes, DMP (DUF679 membrane proteins) and MTL (MATRILINEAL), have been shown to induce haploid production in several species. Here, we identified and characterized DMP and MTL genes in sweetpotato using gene family analysis. In this study, we identified 5 IbDMPs and 25 IbpPLAs. IbDMP5 and IbPLAIIs (IbPLAIIκ, IbPLAIIλ, and IbPLAIIµ) were identified as potential haploid induction (HI) genes in sweetpotato. These results provide valuable information for the identification and potential function of HI genes in sweetpotato and provide ideas for the breeding of DH lines.

Genome-wide systematic survey and analysis of the RNA helicase gene family and their response to abiotic stress in sweetpotato.

Sweetpotato (Ipomoea batatas (L.) Lam.) holds a crucial position as one of the staple foods globally, however, its yields are frequently impacted by environmental stresses. In the realm of plant evolution and the response to abiotic stress, the RNA helicase family assumes a significant role. Despite this importance, a comprehensive understanding of the RNA helicase gene family in sweetpotato has been lacking. Therefore, we conducted a comprehensive genome-wide analysis of the sweetpotato RNA helicase family, encompassing aspects such as chromosome distribution, promoter elements, and motif compositions. This study aims to shed light on the intricate mechanisms underlying the stress responses and evolutionary adaptations in sweetpotato, thereby facilitating the development of strategies for enhancing its resilience and productivity. 300 RNA helicase genes were identified in sweetpotato and categorized into three subfamilies, namely IbDEAD, IbDEAH and IbDExDH. The collinearity relationship between the sweetpotato RNA helicase gene and 8 related homologous genes from other species was explored, providing a reliable foundation for further study of the sweetpotato RNA helicase gene family's evolution. Furthermore, through RNA-Seq analysis and qRT-PCR verification, it was observed that the expression of eight RNA helicase genes exhibited significant responsiveness to four abiotic stresses (cold, drought, heat, and salt) across various tissues of ten different sweetpotato varieties. Sweetpotato transgenic lines overexpressing the RNA helicase gene IbDExDH96 were generated using A.rhizogenes-mediated technology. This approach allowed for the preliminary investigation of the role of sweetpotato RNA helicase genes in the response to cold stress. Notably, the promoters of RNA helicase genes contained numerous cis-acting elements associated with temperature, hormone, and light response, highlighting their crucial role in sweetpotato abiotic stress response.

Systematic identification and expression analysis of bHLH gene family reveal their relevance to abiotic stress response and anthocyanin biosynthesis in sweetpotato.

BACKGROUND: bHLH transcription factors play significant roles in regulating plant growth and development, stress response, and anthocyanin biosynthesis. Sweetpotato is a pivotal food and industry crop, but little information is available on sweetpotato bHLH genes. RESULTS: Herein, 227 putative IbbHLH genes were defined on sweetpotato chromosomes, and fragment duplications were identified as the dominant driving force for IbbHLH expansion. These IbbHLHs were divided into 26 subfamilies through phylogenetic analysis, as supported by further analysis of exon-intron structure and conserved motif composition. The syntenic analysis between IbbHLHs and their orthologs from other plants depicted evolutionary relationships of IbbHLHs. Based on the transcriptome data under salt stress, the expression of 12 IbbHLHs was screened for validation by qRT-PCR, and differential and significant transcriptions under abiotic stress were detected. Moreover, IbbHLH123 and IbbHLH215, which were remarkably upregulated by stress treatments, had obvious transactivation activity in yeasts. Protein interaction detections and yeast two-hybrid assays suggested an intricate interaction correlation between IbbHLHs. Besides, transcriptome screening revealed that multiple IbbHLHs may be closely related to anthocyanin biosynthesis based on the phenotype (purple vs. white tissues), which was confirmed by subsequent qRT-PCR analysis. CONCLUSIONS: These results shed light on the promising functions of sweetpotato IbbHLHs in abiotic stress response and anthocyanin biosynthesis.

Novel Multiresistant Osmotin-like Protein from Sweetpotato as a Promising Biofungicide to Control Ceratocystis fimbriata by Destroying Spores through Accumulation of Reactive Oxygen Species.

Osmotin-like proteins (OLPs) play an important role in host-plant defense. In this study, a novel multiresistant OLP (IbOLP1) was screened from sweetpotato (Ipomoea batatas) with a molecular weight of 26.3 kDa. The expression level of IbOLP1 was significantly higher in resistant cultivars than susceptible ones after inoculation with Ceratocystis fimbriata, which causes black rot disease in sweetpotato. The expression of IbOLP1 in Pichia pastoris led to the lysis of yeast cells themselves. The recombinant IbOLP1 displayed antifungal, antibacterial, and antinematode activity and stability. IbOLP1 could restrain the mycelial growth and lyse spores of C. fimbriata, distinctly reducing the incidence of black rot in sweetpotato. The IbOLP1 can trigger the apoptosis of black rot spores by elevating the intracellular levels of reactive oxygen species. Collectively, these findings suggest that IbOLP1 can be used to develop natural antimicrobial resources instead of chemical agents and generate new, disease-resistant germplasm.

Genome-wide identification of the C2H2 zinc finger gene family and expression analysis under salt stress in sweetpotato.

Introduction: The higher plant transcription factor C2H2 zinc finger protein (C2H2-ZFP) is essential for plant growth, development, and stress response. There are limited studies on C2H2-ZFP genes in sweetpotato, despite a substantial number of C2H2-ZFP genes having been systematically found in plants. Methods: In this work, 178 C2H2-ZFP genes were found in sweetpotato, distributed randomly on 15 chromosomes, and given new names according to where they were located. These members of the zinc finger gene family are separated into six branches, as shown by the phylogenetic tree. 24 tandem repeats of IbZFP genes and 46 fragment repeats were identified, and a homology study revealed that IbZFP genes linked more regions with wild relative species of sweetpotato as well as rhizome plants like potato and cassava. And we analyzed the expression patterns of IbZFP genes during the early development of sweetpotato storage roots (SRs) and salt stress using transcriptome data, and identified 44 IbZFP genes that exhibited differences in expression levels during the early expansion of sweetpotato SRs in different varieties, and 92 IbZFP genes that exhibited differences in expression levels under salt stress in salt tolerant and salt sensitive sweetpotato varieties. Additionally, we cloned six IbZFP genes in sweetpotato and analyzed their expression patterns in different tissues, their expression patterns under abiotic stress and hormone treatment, and subcellular localization. Results and discussion: The results showed that the IbZFP genes had tissue specificity in sweetpotato and were induced to varying degrees by drought and salt stress. ABA and GA3 treatments also affected the expression of the IbZFP genes. We selected IbZFP105, which showed significant differences in expression levels under salt stress and ABA treatment, to be heterologously expressed in Arabidopsis thaliana. We found that IbZFP105 OE lines exhibited higher tolerance to salt stress and ABA stress. This indicates that IbZFP105 can enhance the salt tolerance of plants. These results systematically identified the evolution and expression patterns of members of the C2H2-ZFP gene family in sweetpotato, providing a theoretical basis for studying the role of IbZFP genes in the development of sweetpotato SRs and in resistance to stress.

IbINV Positively Regulates Resistance to Black Rot Disease Caused by Ceratocystis fimbriata in Sweet Potato.

Black rot disease, caused by Ceratocystis fimbriata Ellis & Halsted, severely affects both plant growth and post-harvest storage of sweet potatoes. Invertase (INV) enzymes play essential roles in hydrolyzing sucrose into glucose and fructose and participate in the regulation of plant defense responses. However, little is known about the functions of INV in the growth and responses to black rot disease in sweet potato. In this study, we identified and characterized an INV-like gene, named IbINV, from sweet potato. IbINV contained a pectin methylesterase-conserved domain. IbINV transcripts were most abundant in the stem and were significantly induced in response to C. fimbriata, salicylic acid, and jasmonic acid treatments. Overexpressing IbINV in sweet potato (OEV plants) led to vigorous growth and high resistance to black rot disease, while the down-regulation of IbINV by RNA interference (RiV plants) resulted in reduced plant growth and high sensitivity to black rot disease. Furthermore, OEV plants contained a decreased sucrose content and increased hexoses content, which might be responsible for the increased INV activities; not surprisingly, RiV plants showed the opposite effects. Taken together, these results indicate that IbINV positively regulates plant growth and black rot disease resistance in sweet potato, mainly by modulating sugar metabolism.

Comparative Transcriptome Analysis Reveals the Effect of Lignin on Storage Roots Formation in Two Sweetpotato (Ipomoea batatas (L.) Lam.) Cultivars.

Sweet potato (Ipomoea batatas (L.) Lam.) is one of the most important crops with high storage roots yield. The formation and expansion rate of storage root (SR) plays a crucial role in the production of sweet potato. Lignin affects the SR formation; however, the molecular mechanisms of lignin in SR development have been lacking. To reveal the problem, we performed transcriptome sequencing of SR harvested at 32, 46, and 67 days after planting (DAP) to analyze two sweet potato lines, Jishu25 and Jishu29, in which SR expansion of Jishu29 was early and had a higher yield. A total of 52,137 transcripts and 21,148 unigenes were obtained after corrected with Hiseq2500 sequencing. Through the comparative analysis, 9577 unigenes were found to be differently expressed in the different stages in two cultivars. In addition, phenotypic analysis of two cultivars, combined with analysis of GO, KEGG, and WGCNA showed the regulation of lignin synthesis and related transcription factors play a crucial role in the early expansion of SR. The four key genes swbp1, swpa7, IbERF061, and IbERF109 were proved as potential candidates for regulating lignin synthesis and SR expansion in sweet potato. The data from this study provides new insights into the molecular mechanisms underlying the impact of lignin synthesis on the formation and expansion of SR in sweet potatoes and proposes several candidate genes that may affect sweet potato yield.

Role of Soil and Foliar-Applied Carbon Dots in Plant Iron Biofortification and Cadmium Mitigation by Triggering Opposite Iron Signaling in Roots.

In China, iron (Fe) availability is low in most soils but cadmium (Cd) generally exceeds regulatory soil pollution limits. Thus, biofortification of Fe along with mitigation of Cd in edible plant parts is important for human nutrition and health. Carbon dots (CDs) are considered as potential nanomaterials for agricultural applications. Here, Salvia miltiorrhiza-derived CDs are an efficient modulator of Fe, manganese (Mn), zinc (Zn), and Cd accumulation in plants. CDs irrigation (1 mg mL-1 , performed every week starting at the jointing stage for 12 weeks) increased Fe content by 18% but mitigated Cd accumulation by 20% in wheat grains. This finding was associated with the Fe3+ -mobilizing properties of CDs from the soil and root cell wall, as well as endocytosis-dependent internalization in roots. The resulting excess Fe signaling mitigated Cd uptake via inhibiting TaNRAMP5 expression. Foliar spraying of CDs enhanced Fe (44%), Mn (30%), and Zn (19%) content with an unchanged Cd accumulation in wheat grains. This result is attributed to CDs-enhanced light signaling, which triggered shoot-to-root Fe deficiency response. This study not only reveals the molecular mechanism underlying CDs modulation of Fe signaling in plants but also provides useful strategies for concurrent Fe biofortification and Cd mitigation in plant-based foods.

Modulation of anthocyanin accumulation in storage roots of sweetpotato by transcription factor IbMYB1-2 through direct binding to anthocyanin biosynthetic gene promoters.

The storage roots of purple-fleshed sweetpotato rich in anthocyanins are considered nutrient-rich foods with health effects. However, the molecular mechanism underlying anthocyanin biosynthesis and regulation remains to be revealed. In this study, IbMYB1-2 was isolated from purple-fleshed sweetpotato "Xuzishu8". The phylogenetic and sequence analysis indicated that IbMYB1-2 belongs to the SG6 subfamily with a conserved bHLH motif. Subcellular localization analysis and transcriptional activity assay revealed that IbMYB1-2 is a key transcriptional activator and is specific to the nucleus. Agrobacterium rhizogenes-mediated overexpression of IbMYB1-2 in sweetpotato through in vivo root transgenic system led to an increase in anthocyanins in the root of sweetpotato. qRT-PCR and transcriptome analysis depicted that the transcript levels of IbMYB1-2, IbbHLH42, and eight structural genes that are associated with the synthesis of anthocyanin were upregulated in overexpressed IbMYB1-2 transgenic roots. Dual-luciferase reporter (DLR) assay and yeast one-hybrid (Y1H) assay demonstrated IbMYB1-2 binding to the promoter regions of IbbHLH42 and other anthocyanin biosynthetic genes, including IbCHS, IbCHI, IbF3H, IbDFR, IbANS, IbGSTF12, IbUGT78D2, and IbUF3GT. Moreover, IbbHLH42 was shown to be an active enhancer for the formation of MYB-bHLH-WD40 (MBW) complex, which strongly supports the promoter activities of the IbCHS, IbANS, IbUGT78D2, and IbGSTF12 genes to induce anthocyanin accumulation. Taken together, our findings not only revealed the underlying regulatory molecular mechanism of IbMYB1-2 for anthocyanin accumulation in the storage roots of sweetpotato but also uncovered a potential mechanism by which IbbHLH42 modulated anthocyanin biosynthesis through a positive feedback regulatory loop.

Long-Term Soil Drought Limits Starch Accumulation by Altering Sucrose Transport and Starch Synthesis in Sweet Potato Tuberous Root.

In this study, the influences of long-term soil drought with three levels [soil-relative water content (SRWC) (75 ± 5)%, as the control; SRWC (55 ± 5)%, mild drought; SRWC (45 ± 5)%, severe drought] were investigated on sucrose-starch metabolism in sweet potato tuberous roots (TRs) by pot experiment. Compared to the control, drought stress increased soluble sugar and sucrose content by 4-60% and 9-75%, respectively, but reduced starch accumulation by 30-66% through decreasing the starch accumulate rate in TRs. In the drought-treated TRs, the inhibition of sucrose decomposition was attributed to the reduced activities of acid invertase (AI) and alkaline invertase (AKI) and the IbA-INV3 expression, rather than sucrose synthase (SuSy), consequently leading to the increased sucrose content in TRs. In addition, starch synthesis was inhibited mainly by reducing ADP-glucose pyrophosphorylase (AGPase), granular starch synthase (GBSS) and starch branching enzyme (SBE) activities in TRs under drought stress, and AGPase was the rate-limiting enzyme. Furthermore, soil drought remarkably up-regulated the IbSWEET11, IbSWEET605, and IbSUT4 expressions in Jishu 26 TRs, while it down-regulated or had no significant differences in Xushu 32 and Ningzishu 1 TRs. These results suggested that the sucrose-loading capability in Jishu 26 TRs were stronger than that in Xushu 32 and Ningzishu 1 TRs. Moreover, IbA-INV3, IbAGPS1, IbAGPS2, IbGBSSI and IbSBEII play important roles in different drought-tolerant cultivars under drought stress.

The unique sweet potato NAC transcription factor IbNAC3 modulates combined salt and drought stresses.

Plants often simultaneously experience combined stresses rather than a single stress, causing more serious damage, but the underlying mechanisms remain unknown. Here, we identified the stress-induced IbNAC3 from sweet potato (Ipomoea batatas) as a nucleus-localized transcription activator. IbNAC3 contains a unique activation domain whose MKD sequence confers transactivation activities to multiple other TFs and is essential for the activated expression of downstream target genes. Ectopic expression of IbNAC3 conferred tolerance to single and combined salt and drought stresses in Arabidopsis (Arabidopsis thaliana), and a group of NAM, ATAF1/2, and CUC2 (NAC) TFs, including ANAC011, ANAC072, ANAC083, ANAC100, and NAP, interacted with IbNAC3, and the specific domains responsible for each interaction varied. Intriguingly, IbNAC3 repressed the interaction among the five NACs, and knockout or mutation of ANAC011 and ANAC072 dramatically impaired combined stress tolerance. IbNAC3-ANAC072 and IbNAC3-NAP modules synergistically activated the MICROTUBULE-RELATED E3 LIGASE57 (MREL57) gene. Consistently, mutation of MREL57 and overexpression of WAVE-DAM-PENED2-LIKE7, encoding a target protein of MREL57, both remarkably impaired combined stress tolerance. Moreover, transgenic plants displayed abscisic acid (ABA) hyposensitivity by directly promoting the transcription of ENHANCED RESPONSE TO ABA 1, a key negative regulator of ABA signaling. The data unravel the unique IbNAC3 TF functions as a pivotal component in combined stress tolerance by integrating multiple regulatory events and ubiquitin pathways, which is essential for developing high-tolerant plants in natural environments.

Potassium deficiency causes more nitrate nitrogen to be stored in leaves for low-K sensitive sweet potato genotypes.

In order to explore the effect of potassium (K) deficiency on nitrogen (N) metabolism in sweet potato (Ipomoea batatas L.), a hydroponic experiment was conducted with two genotypes (Xushu 32, low-K-tolerant; Ningzishu 1, low-K-sensitive) under two K treatments (-K, <0.03 mM of K+; +K, 5 mM of K+) in the greenhouse of Jiangsu Normal University. The results showed that K deficiency decreased root, stem, and leaf biomass by 13%-58% and reduced whole plant biomass by 24%-35%. Compared to +K, the amount of K and K accumulation in sweet potato leaves and roots was significantly decreased by increasing root K+ efflux in K-deficiency-treated plants. In addition, leaf K, N, ammonium nitrogen (NH4 +-N), or nitrate nitrogen (NO3 --N) in leaves and roots significantly reduced under K deficiency, and leaf K content had a significant quadratic relationship with soluble protein, NO3 --N, or NH4 +-N in leaves and roots. Under K deficiency, higher glutamate synthase (GOGAT) activity did not increase amino acid synthesis in roots; however, the range of variation in leaves was larger than that in roots with increased amino acid in roots, indicating that the transformation of amino acids into proteins in roots and the amino acid export from roots to leaves were not inhibited. K deficiency decreased the activity of nitrate reductase (NR) and nitrite reductase (NiR), even if the transcription level of NR and NiR increased, decreased, or remained unchanged. The NO3 -/NH4 + ratio in leaves and roots under K deficiency decreased, except in Ningzishu 1 leaves. These results indicated that for Ningzishu 1, more NO3 - was stored under K deficiency in leaves, and the NR and NiR determined the response to K deficiency in leaves. Therefore, the resistance of NR and NiR activities to K deficiency may be a dominant factor that ameliorates the growth between Xushu 32 and Ningzishu 1 with different low-K sensitivities.

A systematical genome-wide analysis and screening of WRKY transcription factor family engaged in abiotic stress response in sweetpotato.

BACKGROUND: WRKY transcription factors play pivotal roles in regulating plant multiple abiotic stress tolerance, however, a genome-wide systematical analysis of WRKY genes in sweetpotato is still missing. RESULTS: Herein, 84 putative IbWRKYs with WRKY element sequence variants were identified in sweetpotato reference genomes. Fragment duplications, rather than tandem duplications, were shown to play prominent roles in IbWRKY gene expansion. The collinearity analysis between IbWRKYs and the related orthologs from other plants further depicted evolutionary insights into IbWRKYs. Phylogenetic relationships displayed that IbWRKYs were divided into three main groups (I, II and III), with the support of the characteristics of exon-intron structures and conserved protein motifs. The IbWRKY genes, mainly from the group Ib, displayed remarkable and diverse expression profiles under multiple abiotic stress (NaCl, PEG6000, cold and heat) and hormone (ABA, ACC, JA and SA) treatments, which were determined by RNA-seq and qRT-PCR assays, suggesting their potential roles in mediating particular stress responses. Moreover, IbWRKY58L could interact with IbWRKY82 as revealed by yeast two-hybrid based on the protein interaction network screening. And abiotic stress-remarkably induced IbWRKY21L and IbWRKY51 were shown to be localized in the nucleus and had no transactivation activities. CONCLUSION: These results provide valuable insights into sweetpotato IbWRKYs and will lay a foundation for further exploring functions and possible regulatory mechanisms of IbWRKYs in abiotic stress tolerance.

Comparative Analysis of Anthocyanin Compositions and Starch Physiochemical Properties of Purple-Fleshed Sweetpotato "Xuzishu8" in Desert Regions of China.

The present study was undertaken to determine the scope of sweetpotato cultivation in arid regions of China. For this purpose, we investigated yield, anthocyanin compositions and physicochemical properties of starch in purple-fleshed sweetpotato (PFSP) "Xuzishu8" under humid (zi8-X) and arid (zi8-D) environments of China. The experiment was conducted in three replications in both environments during 2019 and 2020. The yield and anthocyanidins contents of PFSP were significantly higher in the arid conditions as compared to humid. Zi8-X and zi8-D both revealed the presence of three anthocyanidins, namely, cyanidin (Cy), peonidin (Pn), and pelargonidin (Pg). Cy and Pn accounted for 36.40 and 63.54% of the total anthocyanidins in zi8-X, while in zi8-D, they were found as 26.13 and 73.80%, respectively. The quantitative analysis of these anthocyanins was performed using HPLC-ESI-MS/MS which revealed eighteen anthocyanins such as nine Cy, eight Pn and one Pg. Out of which, eleven anthocyanins showed a significant difference under both conditions. Starch and amylopectin contents were found to be increased by 15.39 and 4.71%, respectively, while the amylose concentration was reduced by 15.54% under the arid environment. The diameter of the starch granule and the peak viscosity were significantly higher under arid as compared to humid conditions. On the basis of results of this study, it seems quite practicable to develop PFSP cultivation in desert regions.

Chromosome painting reveals the genomic structure of three polyploid species of Ipomoea.

Cultivated sweetpotato [Ipomoea batatas (L.) Lam.] from the family Convolvulaceae is a hexaploid species with 2n = 6x = 90 and has been controversial regarding its nature as an autopolyploid arising within a species or an allopolyploid forming between species. Here, we developed oligonucleotide-based painting probes for two chromosomes of I. nil, a model diploid Ipomoea species. Using these probes, we revealed the pairing behavior of homoeologous chromosomes in I. batatas and its two possible polyploid ancestral species, tetraploid I. tabascana (2n = 4x = 60) and hexaploid I. trifida (2n = 6x = 90). Chromosome painting analysis revealed a high percentage of quadrivalent formation in zygotene-pachytene cells of I. tabascana, which supported that I. tabascana was an autotetraploid likely derived by doubling of structurally similar and homologous genomes rather than a hybrid between I. batatas and I. trifida (2x). A high frequency of hexavalent/bivalent and tetravalent pairing was observed in I. trifida (6x) and I. batatas. However, the percentage of hexavalent pairing in I. trifida (6x) was far higher than that in I. batatas. Thus, the present results tend to support that I. trifida (6x) is an autohexaploid, while I. batatas is more likely to be a segmental allohexaploid.